Thermally Induced Loads in Single Ply Membranes

Thermally induced loads in single ply, non-adhered membranes can exert considerable influence on their performance in cold weather. Accurate measurements, however, are difficult to obtain because of the composite nature of the materials. An apparatus was designed and constructed at NRCC that can test four specimens simultaneously for measuring induced loads. The environmental chamber is fitted with four sets of mini-grips and load cells. It is cooled by liquid nitrogen and controlled by a PID controller. The data are stored in a micro computer. Samples of non-reinforced EPDM and reinforced PVC were tested. Different testing protocols were used in order to determine which would provide the most reliable results. It was found that a faster rate of cooling tends to give lower values of load. Cooling in steps gave more consistent average values than lowering the temperature at a constant rate.